"Pressure to meet fast fashion deadlines is leading to women working in Asian factories supplying Gap and H&M being sexually and physically abused, according to unions and rights groups.

More than 540 workers at factories that supply the two retailers have described incidents of threats and abuse, according to two separate reports published last week by Global Labour Justice on gender-based violence in Gap and H&M’s garment supply chains.

The reports claim that these allegations, recorded between January and May this year in Bangladesh, Cambodia, India, Indonesia and Sri Lanka, are a direct result of pressure for quick turnarounds and low overheads.

Publication of the reports comes as negotiations are being held this week at the International Labour Organisation (ILO) to tackle workplace harassment.

Tola Moeun, director of Central Cambodia, an NGO involved in the research, said abuse was a daily reality for female garment workers driven to meet unrealistic targets in H&M and Gap’s supply chains. “Most of these cases are not reported due to fear of retaliation in the workplace.”

Gap and H&M both told the Guardian they would investigate the allegations and that they welcomed initiatives to tackle violence, including an ILO convention.

Jennifer Rosenbaum, US director of Global Labour Justice, said: “We must understand gender-based violence as an outcome of the global supply chain structure. H&M and Gap’s fast fashion supply chain model creates unreasonable production targets and underbid contracts, resulting in women working unpaid overtime and working very fast under extreme pressure.

'Unions and many governments agree an ILO convention on gender-based violence is essential, although there is still opposition from some employers.'

H&M lists 235 Indian garment factories among its suppliers, the report says. In one dispute last month in a Bangalore factory over wages and working conditions, a female tailor said to researchers that she was grabbed by the hair and punched, then told: 'You whore, your caste people should be kept where the slippers are kept.'

One worker in another H&M supplier factory told researchers she was beaten as punishment for not meeting production quotas.

'[My] batch supervisor came up behind me as I was working on the sewing machine, yelling, "You are not meeting your target production." He pulled me out of the chair and I fell on the floor. He hit me, including on my breasts. He pulled me up and then pushed me to the floor again [and] kicked me.'

At an H&M supplier factory in Sri Lanka, one woman complained: 'When girls scold machine operators for touching them or grabbing them, they take revenge. Sometimes they give them machines that don’t function properly. Then they don’t come and repair it for a long time. After that, supervisors scold us for not meeting the target.'"